Our goal is to determine the coordination environment in the inner coordination sphere of Mn2+ site of FosA protein. The hypothesis is that fosfomycin enters the inner coordination sphere of Mn(2+) where it is activated for nucleophilic attack. We believe that fosfomycin displaces 2 or 3 of the water molecules. Broad Mn(2+) EPR lines observed at 35 GHz preclude the use of 17O-labeling methodology to determine the coordination scheme of Mn(2+) in this complex. With an increase in the magnetic field these lines are getting sharper which allows to use 95 GHz (W-band) EPR to study Mn(2+) coordination.